@oniseijin - not true, docs say: "The directFn may also be a string reference to the fully qualified name of the function, for example: 'MyApp.company.GetProfile'. This can be useful when using dynamic loading. The string will be looked up when the proxy is created."

I am using it as a string in my application now and it is necessary in case the JS gets loaded out of order, although I have gotten intermittent errors about the directFn is null whether I use the string or function symbol format